Field of the Invention
Exemplary embodiments of the present invention relate to a thin film transistor, a method for manufacturing the same, and a display substrate using the thin film transistor.
Discussion of the Background
A thin film transistor (TFT) may be used as a switching element for a flat panel display device such as a liquid crystal display or an organic light emitting display. For liquid crystal displays currently commercialized, typical channel layers of the thin film transistors include an amorphous silicon layer, and, in those cases, the field effect mobility (hereinafter “mobility”) of the TFT is about 0.5 cm2/Vs. Technology for high performance TFTs having higher mobility is now desired since the size of displays is getting larger. Therefore, research has been conducted on using oxide semiconductor materials having higher mobilities than the amorphous silicon materials. Some of these materials include ZnO based materials as the channel layer of the TFT. Ga—In—Zn—O, one of the ZnO based materials, exhibits outstanding semiconductor characteristics since its mobility is more than several tens of times greater than the amorphous silicon layer.
However, once such oxide semiconductor material is exposed to external light, changes of its characteristics such as threshold voltage shifts occur, which result in degradation of display quality.